The instant invention is related generally to the use of sabots for guiding sub-caliber projectiles through the barrel of a firearm, and is more specifically directed to an improved sabot bullet or slug for use in connection with shotguns.
Sabot bullets for loading within shotgun shells have heretofore been known, as shown in U.S. Pat. No. 3,726,231, which issued to Kelly et al on Apr. 10, 1973. The above patent discusses the problems associated with providing a sabot bullet for use with a shotgun, and the necessity for the sabot to expand to meet the varying barrel diameters of various shotguns in order to properly guide the bullet therethrough. Although these problems are acknowledged in the above patent, the means employed for solving the same have been found to be inadequate.
With a sabot bullet of the type described in the above patent, proper bullet guidance through a gun barrel depends in large part upon proper spreading of the sabot within the barrel and consequent centering of the bullet guided thereby. In order for the sabot segments to spread and engage the inner walls of a shotgun barrel while maintaining a snug guiding engagement with the bullet, it is necessary that there be rearward movement of the bullet relative to the sabot segments, so as to wedge the sabot segments outwardly against the barrel walls. Without adequate movement between the bullet and sabot, and consequent expansion of the sabot segments, the bullet will not be properly centered in the bore of the shotgun barrel, thereby diminishing the accuracy of the bullet.
The problem with the design of conventional sabot bullets, as shown in the above patent, is that there is little or no allowance provided in the construction of such bullets to allow the necessary relative movement between the bullet and sabot. As can be seen from the sabot bullet in the above patent, the bullet and sabot segments are all initially in abutment with the card wad. Upon firing a shotgun, the direct force of the propellent is applied to the card wad which, in turn, propels the sabot and bullet down the length of the barrel. Since the wad is in initial abutment with both the sabot and the bullet, there can be little or no relative movement between such parts. Consequently, any expansion of the sabot segments is inadequate, if present at all.
Another problem associated with conventional sabot bullets of the type disclosed in the above patent, is that the sabot segments are designed to be in close-conforming, tight-fitting relation with the outer confines of the bullet surrounded thereby. The driving force of the propellent is transfered through the sabot and distributed randomly throughout the entire length of the forward radially diverging portions of the bullet depending on the angular lockup between the sabot and bullet surrounded thereby. The spreading of such forces randomly over a major portion of the bullet surface allows more chance for improper alignment and inbore tipping of the bullet, depending on where the bullet/sabot bearing surface loading takes place. It has been found that the distribution of such forces along the entire forward diverging surface of the bullet is undesirable in that it can provide guidance for the bullet at a point more rearward than desirable, and causes inaccuracies in the flight pattern thereof due to tipping of the bullet in the bore and consequent yaw in flight.
From the above, it is evident that it is desirous to guide the bullet through the barrel of a shotgun from a point near the forward end thereof while simultaneously providing the necessary relative movement between the bullet and sabot segments to provide adequate spreading and wedging of the sabot segments against the inner walls of the shotgun barrel. The instant invention provides an unique construction which meets the above objectives and overcomes the deficiencies previously noted with respect to conventional sabot bullets.